Seal



Aug. 1952 c. M. ALLEN ET AL SEAL 2 SHEETS-SHEET 1 Filed May 25, 1950INVENTORS. Charles M. Allen By Russell W. Dayton AGENTS.

Aug. 5, .1952

C. M. ALLEN ETAL SEAL 2 SHEETSSHEET 2 Filed May 25, 1950 is? f? Ki Q EI\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ INVENTORS. Charles M. Al len RussellW. Dayton AGENTS.

Patented Aug. 5, 1952 ED STATES attain rsNr orrics SEAL , Charles M.Allen; Columbus, and Russell W. Dayton, Worthington, Ohio, assignors, by'mesne assignments, to Battelle Development Corporation, Columbus, Ohio,a corporation' of Dela- Ware Application May 25, 1950, SerialN0.-164,222

able to withstand and for reducingthe leakage pass or through the seal.

In U. S. patents to Richardson, 1,014,850, Masterson et :al., 1,784,104,and Shaw et a1., 2,447,034. are shown centrifugal fluidshaft seals ofrepresentative design with which this invention is generally concerned.Sealing is eifected in these devices by fluid held between thevane orstator and the rotating trough or rotor. As the trough rotates the fluidis thrown outward Claims. (01. 286-9) relates to improvements and buildsup a high pressure between the stator dipping into the fluid and thetrough of the rotor owing to centrifugal force so that it is able towithstand considerable differences in pressure.

The prior art has also shown that certain modip fications are possibleto enable the-seal to be used in a vertical position or when the shaftis stationary. .In such cases double rotors are generally employed whichare driven independently of the shaft, and one ofthe cooperating vanesor I stators is attached to the shaft and may rotate at any independentspeed while the other is secured to the atmosphere or pressure chamber,

wall, etc. One or more pockets or traps in the.

rotors or stators may also be provided to hold the fluid when the systemis not operating in order to prevent its escape from the seal.

It has been found, however, that the maximum benefit in increasedpressure and reduced leakage that might possibly be derived from suchdevices is not achieved due to what is apparently turbuthis turbulenceto enable such seals to be used under conditions of increased pressureor differences in pressure'and'without appreciable leakage, and it is,therefore; an important object of this invention to provide a shaft sealhaving means to reduce the turbulence of the fluid under operatingconditions.

It is another object of this invention to provide a centrifugal shaftseal with baffling to reduce the turbulence of the fluid and therebyenable the seal to be used under conditions of increased pressure withreduced leakage.

It is a further object of this invention to provide for a centrifugalfluid shaft seal, a rotor having in it trough continuous bafflingcharaci 2 terized by reducing the turbulence of the sealing fluid. v o

i It is still further object of this invention to provide the rotor ofacentrifugal shaft seal with a plurality of equally spaced bafflestherein defining pockets for holding a fluid and preventing I turbulencethereof.

These and other objects and advantages of the present invention willbecome more apparent from the following-detailed description anddrawing, in which Figure 1 is a partial vertical, sectional view of arotor and stator of a representative centrifugal shaft seal with thefluid removed and containing the turbulence-reducing baffling of thisinvention, and V t Figure 2 is a vertical, sectional view of thebaffling to be inserted in the trough, and

Figure 3 is a fractional, sectional view of the device shown in Figure1, showing, the relationship of the baffle and thesealing fluid, and

Figure 4. is a fractional, sectional view along the line A-A-of Figure 1showing the pockets formed by the bafiiing, the arrows in the pocketsshowing the current direction of the fluid in the pockets when the rotorand its ba-filing are moving in the indicated direction, and

Figure 5 is a fractional, sectional viewalong the line 0-0 of Figure 1showing the serpentine shape of the baffling; and

Figure 6 is a fractional, sectional view of a portion of the device ofFigure 5 showing the disposition of the fluid relative to the baffling,and Figure 7 is a fractional, sectional view. similar to Figure 5 butshowing a modification of the invention wherein a plurality of bafflesare inserted around the outer portion of the trough of the rotonandFigure 8 is a partial vertical, sectional view "of ons of the insertsdisclosed'in Figure 7.

It has now been discovered that a substantial reduction in turbulence ofshaftseals can be effected resulting in an increase in pressuresobtainable with a reduction in leakage by securing baffling in themoving member of a shaft sealin close proximity to the vane or stator.The baffling creates a plurality of interconnected pockets for thesealing fluid in the trough of the rotor. As thefluid in the troughmoves past the stator,

eddy currents are created in the fluid in each pocket due to the drag onthe fluid by the stator. The currents interfere at the fringes with thecurrents in the adjacent pockets since the common Walls between thepockets are perforated or interconnected. Thus, the turbulence andvelocity of the sealing fluid is reduced, resulting in increasedpressure and reduced leakage.

In general, as shown in the drawing, Figures 1 to 6, the annular rotoris designated as l and has dual fins 2--'-2 and sides or walls 3-3defining internal annular chamber or trough l. The rotor may be drivenindependently of shaft 5 by any means such as a belt or gearing or maybe by suitable gearing connected to the shaft. Spaced about equidistantfrom the internal sides of the rotor and in the trough is annular member6 which as a vane may be secured to the shaft and rotate at a speedrelatively less than said rotor or as a stator may be fixably secured toconcentric sleeve I which is spaced about said shaft and which isattached to wall 8 of a motor housing or atmosphere or vacuum chamber 9.Secured to the rotor in the outer end of the trough throughout itscircumferential length is perforated or screen baffling having agenerally serpentine shape. While in Figure 5, the baffling [0 has beenshown as having a generally serpentine shape with loops-ofroundeddesign, it will be understood that the loops can be of any shape,for example, square or triangular, without departing from the scope ofthe invention or the new and novel results obtained. The baffling iscontinuous about the annular, generally outer portion or periphery ofthe trough and has slot ll extending for a portion of the distance fromits free end or portion into which the vane freely extends.

In operation of the'shaft seal, the mercury I2 which is used as asealing fluid is thrown outward by centrifugal force when the rotormoves, and it lies in the outer portion of the trough formed bythe wallsof the rotor. Due to pressure differences between the outside atmosphereand the vacuum chamber, it occupies positions l3 and I4 of differentheight on either side of the peripheral portion l'of the vane. As shownparticularly in Figure i, the baffling, walls of the rotor, and statorform a plurality of pockets for the mercury, {the pockets beinginterconnected since the bafiling is perforated. As the mercury carriedby the rotor moves past the stator in the direction indicated by thearrows l6l6 frictional forces set up eddy currents, as shown by arrowsll-I'I, in the fluid in each pocket. These currents tend to meet andcounteract each other'by passage through the perforations of thebaflling. In this manner the customary turbulence and velocity 'of themercury is reduced and results in the obtainment of increased pressuresand reduction in leakage during sealing operations. The baiiling must besecured to the rotor and not to the vane or stator for otherwise theopposite effect would be obtained as a great increase in turbulencewould result providing increased leakage and preventing the useof theseal under conditions of even small pressure differentials.

While many methods for inserting the baffling will suggest themselvesreadily to those skilled in the art, it has been found best to firstform screening, made of about 12 gauge nickel wire, in a serpentineshape and weld it to the inside of the rotor in the outer portion of thetrough. After welding, Woods metal is poured in and allowed to solidify.The slot is then machined to the desired dimensions followed by meltingout the Woods metal, leaving the bailiing in place with a continuousannular slot in the portions of the baffling extending away from theperiphery of the trough to enable movement about the vane.

In the modification of the device shown in Figures 7 and 8, separate,arcuate-ended, generally rectangular perforated, baffles or insertsl8-|8 equidistant from each other and parallel to the radii of the rotorare secured to the rotor in the outer portion of the trough. Each baiilehas a slot in which the stator or vane may freely lie, and, thus, theseparate bailles carried by the rotor may move about the stator. Theresults achieved when using a plurality of separate baffles duringoperation of the device are the same as when the. continuous baffling isused.

In securing the individual baffles to the inside of the rotor, groovesl9-i9 are cut in the inside walls of the rotor, and the side edges 20-29of the baffles inserted therein. The baffles may then be welded to therotor or the metal near the grooves mashed or peened to cause it toclose about the baffles. Woods metal is then poured in and thebailiemachined as described supra to provide slots of the desireddimensions. The slots, however, can be cut in the baffles prior toinsertion in the rotor trough if careful machining techniques areobserved.

The baffling material can be of metal or any other material having therequisite strength, capable of being secured to the rotor, and adaptablefor use in centrifugal shaft seals. It must be apertured, porous,perforated, etc., in order that the fluid'in eachpocket can readilycontact the fluid in the adjacent pocket and in order that the fluidwill be in a somewhat continuous fluid mass to provide the necessarysealing under the action of centrifugal force. Examples of preferablematerials are wire screening, perforated metal strips or inserts ofheavy stainless steel, nickel, etc.

The mesh size of the baflling, where screening is used, can be of anysize or number per linear inch provided that substantial interference atthe fringes of the eddy currents is produced, adequate considerationbeing given to the temperature and viscosity of the fluid and the speedof the rotor in order that'the fluid will act as a sealing medium undercentrifugal force. Thus, sizes of from 50 to 400 mesh can readily beemployed, although with mercury and oils, it is preferred to use meshsizes of from to 200.

The baffling disclosed herein is particularly useful with centrifugalfluid shaft seals but can be employed with shaft or other similar sealswherein a stationary or relatively stationary annular member contacts ordips into a flu d which is held by a rotating member and which is underthe influence of substantially centrifugal force and thereby effects aseal between materials at different pressures. Moreover, this inventionis not to be understood as restricted to shaft seals employing only onevane or stator and one rotor but is adaptable for use where a pluralityof vanes and/or stators and rotors are used to effect a sealing actionwhether the rotor, vane, and shaft are independently or dependentlydriven, whether the vane or shaft is stationary or operational, and.whether they are in a vertical or horizontal position or variationthereof. Itis apparent to those skilled in the art that the vane orstator, and also the rotor where necessary, should be accuratelymachined and polished to further reduce any turbulence of the fluid thatmight be caused by surface irregularities, scale,

etc.

Mercury is customarily employed as the sealing fluid or medium andhasbeeniound more desirable when speeds up to' 4 :000"R'. P. M.,are usedin; devices employing the present invention.

However, it is feasible that many other materials can be used as thesealing fluid g flSomegexamples thereof are glycerine, oil, and water.Moreover, low-melting point metalssuch as Babbitt, Woods metal, lead andbismuth can be used as the sealoil or water. Molten salts can also beused alone or in combination with some other fluid; for example,tantalum iodide or perfiuoride could be used on the top of the mercurywhere the shaft seal is being used to seal against gases at lowtemperatures. It is, of course, apparent that some change in dimensionsof the parts of the centrifugal shaft seal may be necessitated wheredifferent speeds and sealing mediums are used.

Tests were made using a centrifugal shaft seal comprising a stationaryvane, a driven rotor, mercury as the sealing fluid, and with and withoutthe bafiling of this invention. Without baffling, the lowest absolutepressure obtainable was 5.5 microns, Whereas with baffling the seal wasable'to sustain a pressure of the order of from 0.15 to 0.50 micronabsolute pressure. Without baffling at 4000 R. P. M., leakage was 158cubic inches of atmospheric pressure air per year, while with bafflingit was 22 cubic inches of atmospheric pressure air per year.

A shaft seal embodying the present invention will find particular use insealing against toxic fumes or vapors, in high-vacuum distillationprocess, in vacuum smelting, in blower shaft seals, etc.

In summary, this invention teaches that the efliciency of a shaft sealcan be greatly increased by providing baifling or bafiles in the troughof the rotor to reduce the fluid turbulence caused by the fluid movingpast the vane. The bafiling or baflies provide interconnected pocketswhere the sealing fluid is partially entrapped although its overallsealing effect under the action of centrifugal force is not adverselyaffected. In this manner, the fluid in each pocket, due to reactionbetween it and the stator, develops eddy currents which interfere at thefringes with the eddy currents of the fluid in the adjacent pockets,thereby reducing the turbulence and increasing pressures obtainable witha comparable reduction in leakage. 7

Having thus described the invention, what is claimed as new and noveland is desired to be secured by Letters Patent is:

1. In a centrifugal fluid shaft seal, the combination of a rotor havingsides defining an internal annular chamber, a sealing fluid adapted tobe held under pressure in the outer portion of said chamber when saidrotor moves, continuous, perforated slotted serpentine baffling securedto said rotor in the outer portion of said chamher, a stator having anannular periphery adapted to contact said fluid whensaid rotor moves andto extend into the slotted portion of said baffling, said baflling, saidstator and the walls of said chamber defining a plurality of spacedpockets therebetween, said pockets inducing interference at the fringesof the eddy currents of said fluid caused by drag on said fluid by saidstator when said rotor and said baffling are moving.

2. In a centrifugal fluid shaft seal, the combination of a rotor havingsides defining an internal annular chamber, a sealing fluid adapted 6.to be held underpr'essurein' the outeigj-portion of said chamberwhen'sai'd rotor 'operatesjcon tinuous perforated serpentine bafilingsecured to three sides of said rotor-in the outer portion of saidchamber, slotsextending from the free portion of said baffling andadapted to receive the annular peripheral portionof a stator, a statordisposed in said chamber and ab'out'which said rotor is designed tomove, anann-ular peripheral portion of said stator 'adaptedrtddip intosaid fluid when said rotor movesand to freely lie in said slots of saidbafiling, 'and,-.said baffles,,,'said stator" and the walls ,of'saidchamber defining a plurality of adjacent interconnected pocketstherebetween, said pockets inducing interference at the fringes of theeddy currents of said fluid caused by drag on said fluid by said statorwhen said rotor and said bafiling are moving and thereby reducing thevelocity and turbulence of said 3. In a centrifugal fluidshaft seal, thecom bination of a rotor having sides defining an internal annularchamber, a sealing fluid adapted to be held under pressure in the outerportion of said chamber when said rotor moves, slotted and perforatedbafilingsecured to said rotor in the outer portion of said chamber, astator having an annular periphery adapted to contact said fluid whensaid rotor moves and to extend into the slotted portion of saidbaffling, said baffling, said stator and the walls of said chamberdefining a plurality of spaced pockets for said fluid.

4. In a centrifugal fluid shaft seal, the combination of a rotor havingsides defining an internal annular chamber, a sealing fluid adapted tobe held under pressure in the outer portion of said chamber when saidrotor moves, a plurality of separate, radially disposed, slotted andperforated bafiles secured to said rotor in the outer portion of saidchamber, a stator having an annular periphery adapted to contact saidfluid when said rotor moves and to extend into the slotted portion ofsaid baffles, said baffles, said stator and the walls of said chamberdefining a plurality of spaced pockets therebetween.

5. In a centrifugal fluid shaft seal, the combination of a rotor havingsides defining an internal annular chamber, a sealing fluid adapted tobe held under pressure in the outer portion of said chamber when saidrotor moves, slotted and perforated bafiling secured to said rotor inthe outer portion of said chamber, an annular. member having a peripheryadapted to contact said fluid when said rotor moves and to extend intothe slotted portion of said baffling; said baffling, annular member andthe walls of said chamber defining a plurality of spaced pocketstherebetween.

6. In a centrifugal fluid shaft seal, the combination defined in claim 5wherein said annular member is a vane attached to the shaft to besealed.

7. In a centrifugal fluid shaft seal, the combination of a plurality ofrotors each having sides defining internal annular chambers, sealingfluid adapted to be held under pressure in the outer portion of saidchambers, when said rotors move, slotted and perforated baffling securedto said rotors in the outer portions of said chambers, a plurality ofannular members each having a periphery adapted to extend into theslotted portion of the baffling in the annular chamber of a rotor and tocontact said fluid when said rotor moves, said baffling, each of saidannular members and the walls or said chamber defining Number aplurality of spaced pockets in each rotor. 876,613 a 999,693 CHARLES M.ALLEN. 1,170,279 RUSSELL W. DAYTON. 5 1,879,626 2,127,865

REFERENCES CITED I The following references are of record in the file ofthis patent: 1 g 2 48 UNITED STATES PATENTS 10 155:953

Number 1 Name Date 822,802 Wilkinson; June 5, 1906 Name Date WilkinsonJan. 14, 1908 Bleaker Aug. 1, 1911 Knourek Feb. 1, 1916 Mendenhall eta1. Sept. 2'7, 1932 Goddard Aug. 23, 1938 FOREIGN PATENTS Country DateGreat Britain Aug. 28, 1906 Germany Dec. 5, 1904

